The present invention relates generally to managing computer storage systems. More particularly the present invention relates to a method, apparatus and computer program for managing computer storage systems having a plurality of different kinds of disk drives that can be attached to the same connector and use different communication protocols.
In recent years, some new communication protocols of computer storage systems have been developed and set as industry standards. For example, Serial Advanced Technology Attachment (SATA) was developed to provide highly scalable architecture to inexpensive large capacity disk drives. Another example is Serial Attached Small Computer System Interface (SAS) was developed to provide high performance and highly reliable Small Computer System Interface (SCSI) drives with serial point-to-point interface and data routing functions.
SAS has numerous enhancements relative to conventional SCSI including, for example, a specification of physical design and protocols to allow SATA drives to be attached to SAS connectors directly. The specification defines how the connector to which a disk drive is attached recognizes what kind of disk drive is being attached. Once the disk drive being attached has been recognized, application programs can read/write data from/to the disk drive according to a specific protocol. By putting SAS drives and SATA drives together into one computer storage system, the system can provide highly reliable and high speed drives as well as inexpensive large capacity disk drives as needed by the situation. Furthermore, the number of SAS and SATA disk drives can be changed flexibly because any SAS connector can be used for a SAS or SATA disk drive. By using a computer storage system which employs SAS architecture, that is a computer storage system that includes SAS and SATA disk drives attached to SAS connectors, users can choose the appropriate storage area to store data according to necessary performance and/or availability.
American National Standard Institute (ANSI) “Project T10/1601-D: Serial Attached SCSI-1.1 (SAS-1.1) (Working Draft)”, Rev. 5, pp 25-42, 26 Jul. 2004 discloses the general architecture of SAS disk drives.
ANSI, “T13 Project 1532D: AT Attachment with Packet Interface-7 Vol. 1—Register Delivered Command Set, Logical Register Set (ATA/ATAPI-7 V1) (Working Draft)”, Rev. 4b, 21 Apr. 2004, and APT Technologies, Inc., Dell Computer Corporation, Intel Corporation, Maxtor Corporation, Seagate Technology, “Serial ATA: High Speed Serialized AT Attachment”, Rev. 1.0a, 7 Jan. 2003, disclose the general architecture of ATA disk drives.
In order to manage, maintain, and make good use of a storage system, administrators must understand the configuration of the system including information of the disk drives: kind (SAS, SATA, etc.), vendor, serial number, capacity, attached port, etc. In addition, if the storage system contains both SAS and SATA disk drives, it is convenient for users to be able to calculate statistical values (total and used capacity, number of errors, performance metrics, etc.) separately for SAS and SATA disk drives. Generally, information of a disk drive is retrieved by sending a command from a controller to the disk drive and receiving a response in a manner specific to the communication protocol the disk drive uses. For example, information of a SAS disk drive is retrieved by sending INQUIRY and READ CAPACITY commands defined by the SCSI protocol. Whereas, information of a SATA disk drive is retrieved by sending an IDENTIFY DEVICE command defined by the ATA protocol. Therefore, a conventional controller which uses one protocol to communicate with disk drives cannot manage a storage system which contains plural kinds of disk drives which use different kinds of communication protocols.